The overall, long-term objective of this research program is to use genetic, immunological and molecular approaches to define the functions that the type 5 and type 12 adenovirus (Ad5 and Ad12) E1A and E1B proteins, and perhaps other viral proteins, play in transforming rat and mouse cells in vitro, and in regulating the events which occur in the early phase of the productive infection in human cells. A particular goal is to understand the basis for the strong oncogenicity of Ad12 in rodents and the striking difference in oncogenicity between that serotype and the non-oncogenic type 5 virus. To this end we have constructed and are characterizing Ad12 and Ad5-based viruses containing chimeric E1A genes, and have used some of these, and point mutants, to identify an oncogenic determinant of Ad 12 located to the spacer region between conserved regions 2 and 3 of the E1A gene. The specific aims of this program over the next five years are to: a. Continue phenotypic analysis of the Ad12-based viruses with chimeric E1A genes, and of rat and mouse cells transformed by these viruses, with a view to defining the potential influence of the E1A spacer region on immunological and other host-related factors which help to shape transformed cell tumorigenicity. b. Continue mutational analysis of the Ad12 E1A nonconserved spacer region which acts as a determinant of oncogenicity. c. Expand the chimeric approach to determine if other E1A regions are required for oncogenicity. d. Carry out phenotypic analysis of the Ad5-based chimeric viruses which carry the Ad12 spacer region and other regions, and determine if the spacer segment can act autonomously. e. Define the molecular basis for the role of the Ad12 E1A spacer region in oncogenic transformation. f.Assess the roles of the Ad5 and Ad12 E1B 55K proteins in oncogenicity. g. Determine if the products of viral genes outside the El transforming region influence the oncogenic capacity of Ad5 and Ad12. h. Explore the basis for the strong susceptibility of Hooded Lister rats to tumor induction by Ad12.